2AAL image
Entry Detail
PDB ID:
2AAL
Keywords:
Title:
Crystal Structures of the Wild-type, Mutant-P1A and Inactivated Malonate Semialdehyde Decarboxylase: A Structural Basis for the Decarboxylase and Hydratase Activities
Biological Source:
Source Organism:
PDB Version:
Deposition Date:
2005-07-13
Release Date:
2005-11-22
Method Details:
Experimental Method:
Resolution:
1.65 Å
R-Value Free:
0.23
R-Value Work:
0.18
R-Value Observed:
0.18
Space Group:
P 32
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Malonate semialdehyde decarboxylase
Chain IDs:A, B, C, D, E, F
Chain Length:130
Number of Molecules:6
Biological Source:Pseudomonas pavonaceae
Ligand Molecules
Primary Citation
Crystal Structures of the Wild-Type, P1A Mutant, and Inactivated Malonate Semialdehyde Decarboxylase: A Structural Basis for the Decarboxylase and Hydratase Activities
Biochemistry 44 14818 14827 (2005)
PMID: 16274229 DOI: 10.1021/bi051383m

Abstact

Malonate semialdehyde decarboxylase (MSAD) from Pseudomonas pavonaceae 170 is a tautomerase superfamily member that converts malonate semialdehyde to acetaldehyde by a mechanism utilizing Pro-1 and Arg-75. Pro-1 and Arg-75 have also been implicated in the hydratase activity of MSAD in which 2-oxo-3-pentynoate is processed to acetopyruvate. Crystal structures of MSAD (1.8 A resolution), the P1A mutant of MSAD (2.7 A resolution), and MSAD inactivated by 3-chloropropiolate (1.6 A resolution), a mechanism-based inhibitor activated by the hydratase activity of MSAD, have been determined. A comparison of the P1A-MSAD and MSAD structures reveals little geometric alteration, indicating that Pro-1 plays an important catalytic role but not a critical structural role. The structures of wild-type MSAD and MSAD covalently modified at Pro-1 by 3-oxopropanoate, the adduct resulting from the incubation of MSAD and 3-chloropropiolate, implicate Asp-37 as the residue that activates a water molecule for attack at C-3 of 3-chloropropiolate to initiate a Michael addition of water. The interactions of Arg-73 and Arg-75 with the C-1 carboxylate group of the adduct suggest these residues polarize the alpha,beta-unsaturated acid and facilitate the addition of water. On the basis of these structures, a mechanism for the inactivation of MSAD by 3-chloropropiolate can be formulated along with mechanisms for the decarboxylase and hydratase activities. The results also provide additional evidence supporting the hypothesis that MSAD and trans-3-chloroacrylic acid dehalogenase, a tautomerase superfamily member preceding MSAD in the trans-1,3-dichloropropene degradation pathway, diverged from a common ancestor but retained the key elements for the conjugate addition of water.

Legend

Protein

Chemical

Disease

Primary Citation of related structures